1. Technical Field
The present invention relates to Group-III nitride crystal substrates advantageously employed in light-emitting devices, and to light-emitting devices and methods of their manufacture.
2. Description of the Related Art
Group III nitride crystal substrates find tremendous utility as substrates for a variety of semiconductor devices including optoelectronic device elements and electronic devices. Improving the characteristics of the variety of semiconductor devices in which III nitride crystal substrates are employed mandates that the substrates be of low dislocation density and favorable crystallinity. Furthermore, from a III nitride crystal substrate use-efficiency perspective, a substrate major-face surface area of 10 cm2 or more, preferably 20 cm2 or more, is deemed necessary.
Therefore, various techniques for fabricating low-dislocation-density III nitride crystal substrates in bulk have been proposed. (Cf., for example, Japanese Unexamined Pat. App. Pub. No. 2007-161536.)
Therein, Japanese Unexamined Pat. App. Pub. No. 2007-161536 discloses that electronic devices including an AlxGayIn1-x-yN (0≦x, 0≦y, x+y≦1) crystal substrate in which the total dislocation density is from 1×102 cm−2 to 1×106 cm−2, and an at least single-lamina semiconductor layer formed onto the substrate have uniform, high breakdown voltages. The document also discloses that from the perspective of heightening the device breakdown voltage, screw-dislocation density in the substrates for the electronic devices is preferably 1×104 cm−2 or less.
Nevertheless, as to correlations between substrate dislocation density and the characteristics of semiconductor devices apart from electronic devices (light-emitting devices for example), Pat. App. Pub. No. 2007-161536 stops short of clarity.